low pressure -filled up and have put too much in ...still very low water fr?

You are confusing water pressure with boiler system pressure, you have over-filled the system pressure in your heating system, make sure you have turned off the valves on the filling loop, the pressure relief valve (prv) will continue to leak until the pressure drops below 3 bar and (if you're lucky) you may not have blown the prv, that should then stop leaking.
For future reference, the system pressure should be 1 to 1.5 bar (when the system is cold).

As for your water pressure, I have no idea, you obviously have plenty of cold mains pressure to blow the prv in the first place, maybe an isolation valve in the cold supply to the bolier is restricting the flow?

Carefree
July 2010